This invention relates to a tool changing mechanism for a numerically controlled machine.
Automatic tool changers are used to remove an old tool from a machine spindle and place it in a tool storage magazine, and take a new tool from the tool storage magazine and place it into the machine spindle.
In machine tools such as machining centers, a workpiece is machined by many tools. For instance, 60 tools or more must be stored in a tool storage magazine. Thus, the tool storage magazine is normally large in size.
A large tool storage magazine cannot be set near a machine spindle, but must be set reasonably apart from the machine spindle.
In a conventional automatic tool changer having a double arm construction, an arm takes a new tool from the tool storage magazine and transfers it to the machine spindle. While the arm grips the new tool, it also grips an old tool and withdraws it from the machine spindle. After that, the positions of the new and old tools are exchanged, and then the new tool is inserted into the machine spindle. The old tool is returned to a specific station in the tool storage magazine.
The problem with such conventional automatic tool changers is that the size must be large in order to control precisely many complicated motions of the arm while the tool is transferred over a long distance.
On the other hand, some conventional automatic tool changers are directly attached to a machine tool body. Each axis of tools stored in a tool storage magazine is parallel to the axis of the machine spindle. In such cases, the tool changing operations cannot be easily controlled.